I'm pretty much done with the project. Here's the latest gameplay video. There's no much visual difference but main gameplay elements are more refined. For example the Remnants can only be dissolved by clicking on actually visible parts. There's now also the damage to the player from direct sunlight. The light generally more dangerous but replenish rates are also higher.
I removed the objective to close all the doors as it seemed a bit tedious. So only windows need to be closed.
The player can escape an encounter with a Remnant in a short period of time while the last window closing animation is playing. In that case the Remnant occupies the room and any subsequent re-entering will instantly kill the player. It's a neat tactical mechanic allowing the player to close the room without inspecting it with light, at the cost of making the room unreachable afterwards. It started as a bug that has grown into a feature :)